Align the job execution result fetching timeout in CollectResultFetcher with akka timeout

Currently in CollectResultFetcher, the job execution result will be fetched after job's termination. In FLINK-17735, we arbitrarily introduce a static timeout for this rpc call. However, in OLAP scenario, the Dispatcher endpoint might be too busy to reply in time. We'd like to set it according to the akka ask timeout, which is commonly used as rpc timeout in Flink.